Facts About Blood: Functions, Types, and Disorders

Explore what blood is, its vital functions, components, blood types, disorders, and how it keeps your body thriving every day.

By Medha deb

Created on Oct 3, 2025

Explore what blood is, its vital functions, components, blood types, disorders, and how it keeps your body thriving every day.

Facts About Blood

Blood is a remarkable and complex fluid that sustains life. It flows tirelessly through your circulatory system, delivering essential nutrients and oxygen, defending against disease, and carrying away waste. Understanding blood’s many functions, its composition, blood types, and common disorders is crucial to appreciating how your body maintains health and responds to illness.

What Is Blood?
Functions of Blood
Main Components of Blood
How Blood Circulates in the Body
Blood Types and Compatibility
Common Blood Disorders
Interesting Facts About Blood
Frequently Asked Questions (FAQs)

What Is Blood?

Blood is a unique type of connective tissue composed of cells suspended in a liquid matrix called plasma. It accounts for about 7% to 8% of your total body weight and is essential for nearly every bodily function.

Total blood volume in adults: Approximately 5 to 6 liters (about 1.3 to 1.6 gallons).
Color: Blood is bright red when oxygen-rich (arterial blood) and dark red when carrying less oxygen (venous blood).

As the main transport system in the body, blood flows through veins and arteries under the steady rhythm set by the heart.

Functions of Blood

Blood’s responsibilities go far beyond just moving oxygen around. Key functions include:

Transportation
- Supplies oxygen from the lungs to tissues and removes carbon dioxide for exhalation.
- Delivers nutrients (like glucose, amino acids, vitamins, and minerals) from digestion to cells.
- Carries metabolic waste products to kidneys and liver for disposal.
Regulation
- Helps maintain body temperature by distributing heat.
- Balances pH (acidity/alkalinity) of body fluids.
- Controls levels of water and electrolytes.
Protection
- Contains immune cells (white blood cells) that fight infection and germs.
- Includes platelets and clotting factors to heal wounds and prevent dangerous bleeding.

Main Components of Blood

Blood is made up of two primary parts: a liquid called plasma and three main types of cells. Together, they enable blood to perform its vital tasks.

Component	Description	Main Function	Percentage of Total Blood Volume
Plasma	Pale yellow liquid; mostly water, with dissolved proteins, hormones, electrolytes, and waste.	Transports nutrients, hormones, proteins, and waste.	About 55%
Red Blood Cells (RBCs) (Erythrocytes)	Disc-shaped cells containing hemoglobin.	Carry oxygen to tissues and remove carbon dioxide.	About 40-45%
White Blood Cells (WBCs) (Leukocytes)	Many types including neutrophils, lymphocytes, monocytes, eosinophils, and basophils.	Defend the body against infection and disease.	About 1%
Platelets (Thrombocytes)	Small, disc-shaped cell fragments.	Help with blood clotting to stop bleeding.	Less than 1%

Plasma

Plasma is about 90% water and contains essential proteins such as albumin, globulins, and clotting factors. It acts as the blood’s transport medium and keeps blood flowing smoothly.

Red Blood Cells (Erythrocytes)

Red blood cells are the most numerous cell type in blood. Packed with hemoglobin, they transport oxygen from the lungs to tissues and return carbon dioxide back to the lungs for removal. Each RBC lives about 120 days.

White Blood Cells (Leukocytes)

White blood cells are crucial defenders against infection. There are several types, each with unique roles:

Neutrophils: Respond quickly to infection, engulfing bacteria and fungi.
Lymphocytes: Includes B-cells (produce antibodies) and T-cells (attack infected cells).
Monocytes: Swallow and digest germs and dead cells.
Eosinophils and Basophils: Help in allergic responses and fight parasites.

Platelets (Thrombocytes)

Platelets are not true cells, but tiny fragments of larger cells called megakaryocytes. When you are injured, platelets clump together at the wound site, forming a plug to seal off bleeding. They also release chemicals to help blood clot effectively.

How Blood Circulates in the Body

Your circulatory system is driven by the heart and a vast network of blood vessels. Here’s how blood flows:

Arteries carry oxygen-rich blood away from the heart to tissues.
Capillaries, the smallest vessels, enable exchange of gases, nutrients, and wastes between blood and tissues.
Veins then return oxygen-poor blood back to the heart.

The cycle repeats with every heartbeat, ensuring cells receive the essentials they need 24/7.

Blood Types and Compatibility

Everyone belongs to a specific blood type, determined by certain antigens on the surface of red blood cells. The two main systems are the ABO system and the Rh (Rhesus) factor.

The ABO Blood Group System

Type A: Has A antigens, anti-B antibodies in plasma.
Type B: Has B antigens, anti-A antibodies in plasma.
Type AB: Has both A and B antigens, no anti-A or anti-B antibodies in plasma.
Type O: No A or B antigens; has both anti-A and anti-B antibodies in plasma.

The Rh Factor

Rh-positive (Rh+): Has the Rh antigen; most people are Rh-positive.
Rh-negative (Rh-): Lacks the Rh antigen; can cause problems in pregnancy or blood transfusion if incompatible.

Blood Type	Can Receive From	Can Donate To
O-	O-	All types (universal donor)
O+	O-, O+	O+, A+, B+, AB+
A-	O-, A-	A-, A+, AB-, AB+
A+	O-, O+, A-, A+	A+, AB+
B-	O-, B-	B-, B+, AB-, AB+
B+	O-, O+, B-, B+	B+, AB+
AB-	O-, A-, B-, AB-	AB-, AB+
AB+	All types (universal recipient)	AB+

Transfusion Compatibility

For a safe blood transfusion, donor and recipient blood types must be compatible.
Receiving incompatible blood can lead to severe, sometimes life-threatening reactions.
Type O- is the universal donor; type AB+ the universal recipient.

Common Blood Disorders

Blood-related disorders can disrupt the functions mentioned above, impacting every aspect of health. Major categories include:

Anemia

Occurs when red blood cell count or hemoglobin levels are too low.
Causes fatigue, weakness, shortness of breath, pale skin.
Types: iron-deficiency anemia, vitamin B12 deficiency anemia, sickle cell anemia, and more.

Clotting Disorders

Hemophilia: Inherited disorder marked by lack of clotting factors, leading to prolonged bleeding.
Von Willebrand disease: Another genetic bleeding disorder.
Deep vein thrombosis (DVT) / Pulmonary embolism: Dangerous blood clots in veins or lungs.

Leukemia and Lymphoma

Leukemia: Cancer of white blood cells, resulting in abnormal, non-functioning cells crowding out healthy ones.
Lymphoma: Cancer of lymphatic (immune) system, affecting white blood cells called lymphocytes.

Platelet Disorders

Thrombocytopenia: Low platelet count, causing easy bruising, frequent bleeding.
Thrombocythemia: Too many platelets, raising the risk of clotting events.

Other Disorders

Sickle cell disease: Inherited condition causing misshapen red blood cells; leads to anemia, pain, and organ damage.
Myeloma: Cancer of plasma cells (a type of white blood cell in bone marrow).

Interesting Facts About Blood

You have about 6 quarts (5 to 6 liters) of blood in your body.
The average red blood cell circulates around your body in roughly 30 seconds.
Blood makes up about 7-8% of total body weight.
Red blood cells outnumber white blood cells by about 600 to 1.
Healthy bone marrow produces around 2 million red blood cells every second.
The first successful human blood transfusion was performed in 1818.
Blood is always red, just a brighter shade when oxygenated.

Frequently Asked Questions (FAQs)

Q: Can you live without all of your blood?

A: No. Blood is essential for transporting oxygen, nutrients, hormones, and immune cells. Loss of more than 40% can be fatal without immediate intervention.

Q: How often can blood be donated?

A: Healthy adults can typically donate whole blood every 56 days (8 weeks). Platelets or plasma donations may be done more frequently.

Q: What are the symptoms of anemia?

A: Fatigue, weakness, pale or yellowish skin, irregular heartbeats, shortness of breath, and dizziness are common signs.

Q: Why is it important to know your blood type?

A: In emergencies or when receiving transfusions, matching blood type is vital to avoid dangerous reactions.

Q: Can blood disorders be inherited?

A: Yes, many blood disorders—such as sickle cell disease, hemophilia, and others—are inherited from family members.

Q: How does blood help fight infections?

A: White blood cells in blood identify, target, and eliminate bacteria, viruses, and other harmful invaders, forming a major part of the immune response.

Conclusion

Blood is so much more than just a red fluid flowing through our bodies—it’s a life-sustaining system that defends, nourishes, and regulates every tissue. Understanding its components, types, and potential disorders is key to managing your health, supporting others through donation, and recognizing the signs of disease early. Stay informed, and appreciate each heartbeat that powers your remarkable circulatory system.

References

Author

medha deb

Medha Deb is an editor with a master's degree in Applied Linguistics from the University of Hyderabad. She believes that her qualification has helped her develop a deep understanding of language and its application in various contexts.

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